Direct Observation of Large Flexoelectric Bending at the Nanoscale in Lanthanide Scandates

There
is a growing interest in the flexoelectric effect, since
at the nanoscale it is predicted to be very large. However, there
have been no direct observations of flexoelectric bending consistent
with current theoretical work that implies strains comparable to or
exceeding the yield strains of typical materials. Here we show a direct
observation of extraordinarily large, two-dimensional reversible bending
at the nanoscale in dysprosium scandate due to the converse flexoelectric
effect, with similar results for terbium and gadolinium scandate.
Within a transmission electron microscope, thin features bend up to
90° with radii of curvature of about 1 μm, corresponding
to very large nominal strains. Analysis including independent experimental
determination of the flexoelectric coefficient is semiquantitatively
consistent with interpreting the results as due to flexoelectricity.
These results experimentally demonstrate large flexoelectric bending
at the nanoscale.